PG&E spokeswoman Katie Romans said a Marin County public works crew using a backhoe struck and ruptured a 2-inch gas line around 8:20 a.m.
A repair crew was sent to the site of the leak, near Civic Center and Peter Behr drives, and stopped the leak shortly after 10:30 a.m., Romans said.
She said no evacuations were necessary, as the rupture occurred in the middle of a field. The incident disrupted gas service to a nearby maintenance building, she said.
Romans said residents worried about the smell are welcome to call PG&E with any questions.
"We want customers to know that this is taking place, and if they have any concerns at all, they can call our hotline at (800) 743-5000," she said.
Crews were still at the scene making permanent repairs as of 10:45 a.m.
Romans said PG&E is asking anyone planning a digging project to call 811 beforehand to make sure the digging doesn't affect underground gas lines.